Organocatalyzed Michael addition of acetone to β-nitrostyrene^a.

Entry	Cat	T	% convb	e. r.c
1	4	NO	<5	—
2	6a	NO	55	57 : 43
3	6b	NO	28	54 : 46
4	4	YES	17	57 : 43
5	6a	YES	85	78 : 22
6	6b	YES	95	91 : 9
7	—	YES	0	0

^aReaction conditions: acetone (0.25 mmol), β-nitrostyrene (0.025 mmol), catalyst (10 mol%), N-hexylthymine (0 or 0.125 mmol), CH₂Cl₂ (100 μL), 25 °C, 5 days.

^bDetermined by ¹H NMR from the crude reaction.

^ce. r. determined by HPLC using a Daicel ChiralPak AS-H column.